An adventure game, of the old style with a plot to solve, like Police Quest, Rise of the Dragon, Space Quest, Pandora Directive, and such, but with 3D graphics in the style of a first person shooter game (like CoD, Quake, Halo, and such), and, why not, some chances to be involved in the ocassional shootout (in fuller FPS mode, but only as a rare break from plot solving, like old adventures would have some action sequence or logic puzzle to solve, not as a big part of the game)...

Don't know why they never really merged adventure games with FPS graphics...